Specifies the step size for tuning the local oscillator (LO) phase-locked loop (PLL).

When the LO PLL Fractional Mode Enabled property is set to Enabled, the specified step size affects the fractional spur performance of the device. When the LO PLL Fractional Mode Enabled property is set to Disabled, the specified step size affects the phase noise performance of the device.

Supported Devices: PXIe-5644/5645/5646, PXIe-5830/5831/5832/5840/5841/5842

Default Values:

PXIe-5644/5645/5646: 200 kHz

PXIe-5830: 2 MHz

PXIe-5831/5832 (RF port): 8 MHz

PXIe-5831/5832 (IF port): 2 MHz, 4 MHz

PXIe-5840/5841:

  • Fractional mode: 500 kHz
  • Integer mode: 10 MHz for frequencies less than or equal to 4 GHz. 20 MHz for frequencies greater than 4 GHz.

PXIe-5841 with PXIe-5655: 500 kHz

PXIe-5842: 1 Hz

Valid Values:

The valid values for this property depend on the LO PLL Fractional Mode Enabled property.

PXIe-5644/5645/5646—If you set the LO PLL Fractional Mode Enabled property to Disabled, the specified value is coerced to the nearest valid value.

PXIe-5840/5841—If you set the LO PLL Fractional Mode Enabled property to Disabled, the specified value is coerced to the nearest valid value that is less than or equal to the desired step size.

To use this property for the PXIe-5830/5831/5832 and PXIe-5842 VST with 54 GHz Frequency Extension, you must first use the Active Channel property to specify the name of the channel you are configuring. You can configure LO1 and LO2 channels by using lo1 or lo2 as the channel string, or set the channel string to lo1,lo2 to configure both channels. For all other devices, the only valid value for the channel string is "" (empty string).

Note For any PXIe-5842 instrument without frequency extension (i.e. no RMM-5585 remote measurement module connected), the only valid value for the channel string is "" (empty string).
LO PLL Fractional Mode Enabled Property Setting LO Frequency Step Size Property Valid Values on PXIe-5644/5645 LO Frequency Step Size Property Valid Values on PXIe-5646 LO Frequency Step Size Property Valid Values on PXIe-5840/5841 LO Frequency Step Size Property Valid Values on PXIe-5830/5831/5832 LO Frequency Step Size Property Valid Values on PXIe-5841 with PXIe-5655, PXIe-5842*
Enabled 50 kHz to 24 MHz 50 kHz to 25 MHz 50 kHz to 100 MHz LO1: 8 Hz to 400 MHz

LO2: 4 kHz to 400 MHz		 1 nHz to 50 MHz
Disabled 4 MHz, 5 MHz, 6 MHz, 12 MHz, 24 MHz 2 MHz, 5 MHz, 10 MHz, 25 MHz 1 MHz, 5 MHz, 10 MHz, 25 MHz, 50 MHz, 100 MHz LO1: --

LO2: --		 1 nHz to 50 MHz
Note * Values up to 100 MHz are coerced to 50 MHz.

Remarks

The following table lists the characteristics of this property.

Short Name LO Frequency Step Size (Hz)
Data type cdbl.png
Permissions Read/Write
High-level VIs N/A
Channel-based Yes
Resettable Yes